678 MR. R. I. POCOCK ON THE EXTERNAL 



no tvace of the pair of long spikes seen in the latter species. 

 According to the descriptions of Olivier and Tullberg the glans 

 penis of AUactaga saliens closely resembles that of Scarturus. 

 (Text-fig. 36, K, L.) 



The anus and genitalia of the male of Pedetes ca-ffer were 

 described and figured by Calori *. To his account Tullberg had 

 nothing to add. The anus is situated a long way below the root 

 of the tail, much farther than in the Jaculidae, and the prepuce 

 of the retroverted penis forms a conical prominence beneath it. 

 Superficially the anus appears as a crescentic slit, with the 

 concavity downwards ; and this appearance results from the 

 downward growth of the skin of its upper border forming a 

 flap over the anus itself. Calori described a gland-opening in 

 the middle line of the perineum between the anus and the penis. 

 This does not appear to me a very appropriate description, 

 because no orifice is visible on the area named. There is, how- 

 ever, the orifice of a gland-opening within the prepuce just above 

 the urino-genital orifice when the penis is retroverted and at 

 rest. The penis itself is elongated, compressed, and covered 

 with minute spicules ; but there is no trace in it of the 

 glandular pouch which is so characteristic of the Hystricomorphs. 

 (Text-fig. 36, M.) 



a. A large gland-opening within the prepuce of the male on the anal 

 side of the genito-urinary orifice ; anus in the form of a crescentic 



slit some distance above the iienis Fedetes. 



a'. No preputial gland on the anal side of the genito-urinary orifice of 

 the penis ; anus not ci'escentic in shape. 

 h. Anus exposed above the tip of the penis, which is not tucked up 



against it ... ; Za-fus. 



h' . Anus concealed beneath an excrescence, to the under side of which 

 the tip of the penis is applied. 



c. Glans penis spiny with two immense erectile spikes Scirtopoda> 



c' . Glans penis without spikes. 



d. Glans penis elongated, parallel-sided, covered with mimite 



pits, each provided with a serrate scale Jaculus. 



d' . Glans penis ovate, armed with spines Scarturus, AUactaga. 



The Skull o/ Scarturus. 



The skull and dentition of Scarturus agi-ee in essentials with 

 those of AUactaga, and differ in many points from those of 

 Jaculus — that is to say, the incisors are ungrooved and slightly 

 projecting, though not nearly so strongly as in A. indica, for 

 example; the minute upper premolar is retained ; the zj^gomatic 

 arch is comparatively slender where it forms the anterior wall of 

 the orbit ; the channel for the nerve is formed by a deep notch in 

 the floor of the antorbital foramen and not a closed tube as 

 in Jaculus ; the auditory bullse are much less inflated than in 

 Jaculus, despite the large size of the ears, and the mastoid is not 

 visibly inflated. I cannot, indeed, find any generic characters to 



* Mem. Accad. Sci. Bologna, v. pp. 297-298 (1854). ' 



